Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.75	8.595%	$190.8557	$190.86	$190.85	$190.90
Purchase #2	$182.33	12.638%	$205.3729	$205.37	$205.35	$205.40
Purchase #3	$105.57	9.754%	$115.8673	$115.87	$115.85	$115.90
Purchase #4	$129.83	7.578%	$139.6685	$139.67	$139.65	$139.70
Purchase #5	$128.42	11.527%	$143.223	$143.22	$143.20	$143.20
Purchase #6	$199.33	11.258%	$221.7706	$221.77	$221.75	$221.80
Purchase #7	$120.54	9.329%	$131.7852	$131.79	$131.80	$131.80
7 purchase totals =	$1,041.77		$1,148.5432	$1,148.55	$1,148.45	$1,148.70